Not applicable.
1. FIELD OF INVENTION
The invention relates to apparatus and methods of automated photo image scanning for photo reprographics from various slide transparency, negative film, and reflective print media. More particularly, the invention is directly applicable to demanding photo-optical applications where scanner equipment is required to image capture at the highest quality image resolution and fidelity possible.
2. DESCRIPTION OF RELATED ART
Analog film with its infinite color representation and optical emulsion continuous tone fidelity has been traditionally an extremely good source for high quality image reproduction. This work, historically, was performed by analog photo optical techniques. For instance, one extreme example is the case of film placed in a large optical projection camera, which is then constructed into a large darkroom, and optically exposing to large format photo paper. This kind of application for film has for years been used to create many of today""s photo KIOSKS or large format photo advertising banners. Other high quality photography and film applications have included school and portrait photography, pre press, motion pictures, and thousands of other professional uses of film as tooling for image reproduction.
It has always been an industry difficulty, even before the advent of digital imaging, to obtain accurate photo reproduction color and optical quality. This gave rise to the use of video cameras and scanners as colorimeters for determining the corrected values to be used in the analog reproduction process. U.S. Pat. No. 3,893,166 to Pugsley (1975). Color correcting image reproduction method and apparatus.
With the advent and proliferation in recent years of digital imaging output devices, the demand for the higher quality and speed of digital scanning has grown. In general, the tools have not been up to the quality standards for many of the tasks. The highest state of the art has been for a skilled scanner operator to use personal judgement to scan film positive transparencies (slide film). The operator interacts on a computer workstation, with a color monitor, to select scanner parameters and create digital image data files. U.S. Pat. No. 5,155,588 to Levien (1992) discloses a color correction and apparatus for photographic reproduction.
The limitations of this approach are due to many factors. First, the entire approach depends on human judgement, utilizing an inaccurate color monitor to subjectively balance color and set resolution and optical control parameters. The actual quality results will not be totally visible until after printing the media. Additionally, due to the combination of the density to sensitivities of the film with the intensity variations of a scanner, the highest quality processes are limited to only a bump function and only applicable to positive transparency film.
Thereafter, inventors created calibration techniques for color calibrating scanners to attempt to compensate for exposure control with test reflective photography. U.S. Pat. No. 5,721,811 to Eckhardt (1998) discloses a pre press system color control technique which can only scan slide transparencies utilizing an instant color photograph as a photo color reference for lighting conditions. This inventor states that photographic color film transparencies are exclusively used because using negatives with color would add complexity, loss of sharpness, and color distortion to the process. Photo prints are generally inadequate because the image print resolution quality is much lower than film. Negative film is not often used because the scanner and computer equipment is not up to the task. More than 90% of all film sold and used is negative film, yet none of these materials are currently suitable for the high quality digital image reproduction process because of scanning limitations. Negative film densities are reversed, offset in yellow, magenta, and cyan dye densities, and very compressed between the representatives of information content between black and white. Typical spectral density distribution compression is between 35 and 50%, (depending on the type of negative film), making digitizing negative film very sensitive to computer error.
Computer scanners are typically manufactured with log curves built into the equipment in order to approximate (only) film response and to display attractive results to video gamma devices including computer monitors. However, all photo film dye densities are characterized not by log curves, but more generally xe2x80x9cSxe2x80x9d shaped curves that are unique to each material, with shadow and highlight detail fall off Thus, spectral response shadow and highlight details are damaged or lost with log curve scanning.
The digital fidelity scanning color depth process, to the computer from the scanner, is typically controlled by a 24-bit to 36-bit color lookup table (analog to digital converter), and a 24-bit color depth (16.7 million available colors). The color spectral compression of negative film densities has the effect of reducing the scanner intensity data space to be reduced by 35%-50% of the digital domain of the scanner. Therefore, the 24-bit data space is reduced to representative values of between approximately 16 to 12-bit. Thus, the available photo image color space is reduced from the infinite number available on the analog negative film, and the 16.7 million potential colors of the scanner, to the lowest common film to scanner intensity response of the film density. That is between 65,535 to 4096 individual digital color representation for 16 to 12-bit respectively. This often causes visible posterization or duplications of colors in digital image scans of negative film.
Further complicating the photo-media scanner technology state of the art is the fact that not only is every film stock media different in the dye or ink stock that it is formulated with, but also each photographer""s individual exposure of the film can have slight differences in light levels. With highly sensitive films (especially negatives) the color correction curves for each different exposure varies significantly. Therefore, standardized color corrections are not enough to avoid the problems of serious color shifts and aberrations in the results. U.S. Pat. No. 5,475,493 to Yamana (1995) discloses a gray balance correcting method to address this problem. The limitation of this approach is that it is based solely on three points, white/Dmin, black/Dmax, and gray densities. Due to the digital domain data sensitivity issues previously mentioned, it is necessary to have all the data values possible, both to avoid color distortion and to digitally capture to support the full fidelity of the film""s spectral data.
Two types of image processing generalized analysis methods have been proposed. The first, U.S. Pat. No. 5,200,816 to Rose (1993), provides for color processing with learned neural networks based on utilizing KODAK Q60 Targets as a scanner reference. This proposal, based on its dependency on the ISO IT8 sub-committee target standards, as a result lacks all reference to primary colors of red, green, blue, magenta, yellow, and cyan between black and their fully saturated color representation. Additionally, neither KODAK nor other sources provide this target on any photo media except on limited varieties of positive (SLIDE) transparencies and print paper. Thus, the referenced learning color method lacks access and methodology for the color fidelity information necessary for the most demanding applications and is not applicable to negative film altogether.
The second, U.S. Pat. No. 5,748,773 to Tashiro (1998), is a laser copy machine pre-scan operation that detects the material type by looking for a predetermined set of color feature points from the formed histogram of the pre-scan. By comparing the sampled feature points to a second set of feature points, it then converts the data to a third color feature points set. Although pre-sampling the media and performing a histogram analysis gives important artificial intelligence data, how the pre-sample data is used is of equal or even more importance. The proposal is limited in its ability to totally reproduce the accuracy of the analog film because there is a fundamental lack of the complete film characterization knowledge necessary before a sample is taken. In this invention, the sample is used based only on a limited number of feature points for a scan. This approach does not yield an adequate fidelity of information to support the quality necessary for applications demanding film accuracy.
Beyond these discussed color reproduction problems; high quality digital scanning from film is also hampered by the optical film emulsion formulation of its film""s grain structure. Each film type, and even different ASA ratings of the same film, have different dye formulations and optical grain size. When scanned and printed at highly enlarged sizes from a finely focused film scanner, the film grain becomes apparent. This is typically seen as an optically visible interference or noise. When scanning at resolutions of 2000 dots per inch/78 dots per millimeter or higher; this phenomenon is caused by a mismatch between the scanner""s optical digital sampling and focus with that of the analog grain of the film. No prior art has addressed this matter.
Consequently, the current state of the art for professionally demanding applications of digital scanners still has several outstanding problems:
a) Photo scanning is a very subjective, user interpretive, time consuming, error prone, and expensive process.
b) Color accurate digital scanning, calibrated to traditional film professional standards, is very difficult if not impossible for most people to perform.
c) Negative films can generally not be used as a viable digital-imaging source.
d) Professional scanner operators possessing the necessary color science and optical film knowledge are very difficult to find and expensive to employ.
e) With growing industrial use of high quality and large format professional imaging output devices, they can visibly reproduce optical noise and even the sandpaper textures (optical granularity) of the original film when scanned.
f) Due to the current state of the art, the professional image production photo, pre press, and motion picture industries expend substantial amounts of labor and money to digitally touch-up and correct inadequate quality photo scan captures.
The invention is to automatically digitally scan all types of film, photo print media, and imagery at the combined optimized optical and spectral accuracy without human intervention.
Accordingly, besides the time saving advantages of fully automatic image capture and scanning operations as described above, there are several objects and advantages of the present invention:
a) To provide a photo image scanner capture capable of absolute duplication of the optical and color density quality of the original, without human interpretation or intervention.
b) To provide an image media trained artificial intelligence scanner, which is pre-calibrated to professional standards.
c) To provide a photo image scanner capable of accurately scanning all materials: negative film, transparency slides, silver halide photo and ink prints, etc.
d) To provide a fully artificially intelligent color image scanner, that can be used by typical users, and still obtain the imaging industry""s highest quality photo image capture.
e) To provide a photo image scanner where the maximum optical analog film quality is maintained or even enhanced by image scanning, not degraded or made to extenuate film noise artifacts.
Further objects and advantages are to provide a synergistic harmony between the physical digital properties and characteristics of the scanner ability, and the comparable analog properties and characteristics of a photo media - spectral density, grain size, exposure and color response.
It is further the object of this invention to create and maintain a learned knowledge database of film media and scanner equipment optical and color fidelity physical properties. This includes photo and print paper, as well as negative and positive transparency materials, and scanners of all varieties, drum PMT, linear and flatbed, fly spot PMT scanners, and matrix array cameras.
It is further the object of this invention to compute, in real-time during a scan, the unique optical sampling and color correction required by the film being scanned. Applying a dynamically determined correction, as necessary, over the entire spectral response curve of the stored standard film media properties, performs this function.
It is further the object of this invention to dynamically accommodate the optical address-ability of the subject being scanned, including film media grain with the media optical database definition and optimal selection of the scanner equipment device-dependent properties, including aperture lens and sensor array controllability.
It is further the object of this invention to provide maximum optical digital capture of the photo. This is performed by the means of automatic digital sampling of the film media at a sample rate comparable to the maximum optical sample size relative to the physical analog film grain size. This process is applicable to continuous tone film media, screen size for ink-printed media, and other sources.
It is further the object of this invention to not use log exponential, linear, or mathematic gamma color correction curves, but rather, to utilize exclusively the actual physically derived and sensed complex media specific film dye density curves for media color correction standards.
It is further the object of the invention to detect the need for tone correction via presampling of the film and comparing the measured density and intensity values to high fidelity film media specific standard density values pre-stored in media knowledge bases.
It is further the object of this invention to pre-sample scan data, utilize density to intensity and histogram analysis to compute curves of control color points, select the closest match media standard characteristic, and to adjust as required the state of the film media database. Then, based on this process, to use the current state of standard media correction for the scan.
A significant distinguishing advantage of the invention is that, in addition to the labor savings of automatic unattended photo-correct scanning; vast cost savings are derived from avoiding the need for post-production image correction and clean up of bad scans.
Even further objects and advantages will become apparent from a consideration of the ensuing description and drawings.